1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to digital rights management (DRM), and more particularly, to DRM method and apparatus which can effectively manage rights objects.
2. Description of the Related Art
Recently, digital rights management (DRM) has been researched actively and commercial services using DRM have already been implemented or will be implemented. DRM is a technical concept to protect digital content that can be readily copied and distributed without permission.
Some efforts have been made to protect digital content. In a related art, digital content protection has concentrated on preventing those without permission to access digital content. Specifically, only those people who have paid fees are permitted to access the digital content, and persons who have not paid the charges are denied access the digital content. However, the digital content can be readily copied, reused, processed and distributed to third parties according to the characteristics of the digital data. Accordingly, when a person who has paid the fees accesses the digital content and intentionally distributes it to a third party, the third party can use the digital content without paying the fees, which has produced a number of problems.
In order to solve these problems, in DRM, the digital content is encrypted and distributed, and a specified license called a rights object is needed to use the encrypted digital content.
After a media player obtains rights, if the rights object stored in the media player disappears, the media player may, again, request a universal plug and play (UPnP) media server to provide the rights object. Then, the UPnP media server may compare an object ID, which is an identifier of content corresponding to the rights object requested by the media player, and provide the rights object to the media player.
However, if the object ID used to identify the content stored in the media server lapses after a predetermined period of time or if the media server is rebooted, the object ID corresponding to the content may disappear or change. Accordingly, a new object ID may be given to the content. Consequently, the media server cannot find the content corresponding to the rights object requested by the media player and thus cannot provide the rights object to the media player.
In addition, after the media player obtains a rights object from an external DRM system, if the rights object stored in the media player disappears, the media player may request the media server to provide the rights object. However, since an object ID stored in the media server cannot recognize a content ID used to identify content in the external DRM system, the media server cannot find content corresponding to the rights object requested by the media server and thus cannot provide the rights object to the media player.